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In the context of programming and software design, an event refers to an action or incident that is identified by the software. These events can be initiated by the system, user inputs, or other sources and are subject to handling by the software.
Specifically, a close event is an occurrence triggered when a figure is closed within the software interface. This event means the termination or closure of the graphical representation or window associated with the figure and reminds the software to respond accordingly.
Close Events in Matplotlib
Matplotlib provides a set of tools to handle events, among them is the ability to handle close events. A close event in Matplotlib occurs when a figure window is closed, triggering specific actions within your Python script. By connecting to the close_event you can execute custom code in response to a figure being closed.
In this tutorial, we will explore how to use close events in Matplotlib to enhance interactive plots.
Example
Here is a simple example that displays a message when the user closes the figure.
import matplotlib.pyplot as plt def on_close(event): print(''The Figure is Closed!'') fig, ax = plt.subplots(figsize=(7, 4)) ax.annotate(''X'', xy=(1, 1), xytext=(0.9, 0.65), fontsize=20, arrowprops=dict(facecolor=''red''), horizontalalignment=''left'', verticalalignment=''bottom'') fig.canvas.mpl_connect(''close_event'', on_close) ax.text(0.15, 0.5, ''Close This Figure!'', dict(size=30)) plt.show()
Output
On executing the above code we will get the following output −
After closing the above output figure, the following message is displayed in the console −
The Figure is Closed!
Detecting Closed Axes
When dealing with multiple axes in a figure, you need to determine if a specific axis has been closed you can use the close event action in Matlotlib.
Example
Here is an example that demonstrates how to determine if a specific axis has been closed or not, using the close event in Matplotlib.
import matplotlib.pyplot as plt # Function to handle the event def on_close(event): event.canvas.figure.axes[0].has_been_closed = True print(''The Figure is Closed!'') # Create the figure fig, ax = plt.subplots(figsize=(7, 4)) ax.set_title(''Detecting Closed Axes'') ax.has_been_closed = False ax.plot(range(10)) # connect the event with the callable function fig.canvas.mpl_connect(''close_event'', on_close) plt.show() print(''Check the attribute has_been_closed:'', ax.has_been_closed)
Output
On executing the above program you will get the following output −
After closing the above output figure, the following message is displayed in the console −
The Figure is Closed! Check the attribute has_been_closed: True
Continuing Code After Closing
In some cases, it may be necessary for your code to continue running even after the figure is closed (close event triggered). This is particularly useful for background processes or animations.
Example
The following example demonstrates how to continue code execution after the figure is closed.
import matplotlib.pyplot as plt import matplotlib.animation as animation import numpy as np import time close_flag = 0 def handle_close(evt): global close_flag close_flag = 1 print(''The Figure is Closed!'') # Activate interactive mode plt.ion() fig, ax = plt.subplots() # listen to close event fig.canvas.mpl_connect(''close_event'', handle_close) # Generating x values x = np.arange(0, 2*np.pi, 0.01) y = np.sin(x) # Plotting the initial sine curve line, = ax.plot(x, y) ax.legend([r''$sin(x)$'']) # Function to update the plot for each frame of the animation def update(frame): line.set_ydata(np.sin(x + frame / 50)) return line t = 0 delta_t = 0.1 while close_flag == 0: if abs(t - round(t)) < 1e-5: print(round(t)) x = x + delta_t y = y - delta_t # Creating a FuncAnimation object ani = animation.FuncAnimation(fig=fig, func=update, frames=40, interval=30) # draw the figure fig.canvas.draw() fig.canvas.flush_events() # wait a little bit of time time.sleep(delta_t) t += delta_t if close_flag == 1: break print(''ok'')
Output
On executing the above program you will get the following output −
After closing the above output figure, the following message is displayed in the console −
0 1 2 3 4 5 The Figure is Closed! ok
Watch the video below to observe how the close event feature works here.
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